At present, cylinder-shaped or square-shaped lithium battery is widely used in electronic products, such as portable computer, cell phone and music player. The production process of the lithium battery mainly includes the following steps: firstly, winding a positive electrode plate, a negative electrode plate and separators for separating the positive electrode plate from the negative electrode plate into a cylinder-shaped or square-shaped cell core; then, injecting electrolyte into the cell core; finally, introducing a metal shell to seal the cell core. And the step of winding is the most important step in the production process.
The present winding machine for the lithium battery mainly includes two electrode plate supply units, two separator supply units, a separator fixing unit, a winding unit, a cutter and an unloading unit. Two electrode plate supply units and two separator supply units are both disposed above the separator fixing unit. Two separator supply units are disposed on both sides of one electrode plate supply unit. The winding unit is disposed between the two separator supply units and the separator fixing unit. The cutter is disposed under the separator fixing unit and the unloading unit is disposed under the cutter. Specifically, the winding unit mainly includes a mounting seat, a locking cap, a winding assembly and a winding assembly driving mechanism. The locking cap and the winding assembly driving mechanism are fixed to the opposite ends of the mounting seat respectively. One end of the winding assembly is fixed to the winding assembly driving mechanism and the other end thereof is opposite to the locking cap. And the winding assembly is driven to move and rotate about an axis of the winding assembly by the winding assembly driving mechanism. More specifically, the winding assembly includes a pair of flat-shaped winding needles which are overlapped. A rectangular locking hole is formed in the middle of the locking cap. Before winding, the end of the pair of winding needles is inserted into the locking hole and fixed by the locking hole.
During the operation of the winding machine, two separators are supplied to the separator fixing unit by two separator supply units respectively and fixed by the separator fixing unit. The winding assembly is driven to grip one separator by the winding assembly driving mechanism. Then, the starts of the two separators are spliced by a bonding unit. The positive electrode plate and the negative electrode plate are supplied to the separator gripped in the winding assembly from the both sides of the separator by two electrode plate supply units. Meanwhile, the winding assembly is driven to rotate about the axis thereof by the winding assembly driving mechanism. And two separators, the positive electrode plate and the negative electrode plate are wound following the rotation of the winding assembly, thus forming a winding core. After winding, the cutter cuts the two separators, the positive electrode plate and the negative electrode plate. The finished winding core is drawn from the winding assembly and transferred to the next procedure by the unloading unit.
However, on one hand, because the separators, which are used to separate the positive electrode plate from the negative electrode plate to preventing a short circuit therebetween, are too thin, the winding needles which are overlapped cannot grip the separator firmly during the winding process. The separator will draw out from the pair of winding needles, thus bringing the short circuit in the battery. Furthermore, in order to fix the separators to the winding assembly, the starts of two separators are spliced by a bonding unit. In such a manner, the winding process becomes more complicated, thereby reducing the production efficiency of the winding device. On the other hand, since the locking hole formed on the locking cap shapes like a rectangle to locking the winding assembly, the direction of the winding assembly must be adjusted correctly to fit the ends thereof into the locking hole, thus reducing the installation efficiency of the winding device, and thereby reducing the production efficiency of the cell core.
Hence, a need has arisen for providing an improved automatic winding device for cell core to overcome the abovementioned problems.